Display Device

1. A display device, comprising: a display panel including data lines, gate lines which cross the data lines, and pixels; a gamma voltage generator configured to generate first to nth gamma voltages, n being an integer; and a data driver configured to generate data voltages by selecting the gamma voltages according to input image data, and to supply the data voltages to the data lines, wherein the gamma voltage generator comprises: a first voltage dividing unit configured to divide a reference voltage; a first voltage dividing circuit configured to generate the first gamma voltage by selecting voltages output from the first voltage dividing unit according to a highest gamma register value; and a second voltage dividing circuit configured to generate the second to nth gamma voltages using the reference voltage, wherein the gamma voltage generator comprises a red (R) gamma voltage generator, a green (G) gamma voltage generator, and a blue (B) gamma voltage generator, and wherein one of the R gamma voltage generator, the G gamma voltage generator, the B gamma voltage generator is supplied with the highest gamma register value which is different from the highest gamma register value supplied to another of the R gamma voltage generator, the G gamma voltage generator, and the B gamma voltage generator.

2. The display device of claim 1 , wherein the first voltage dividing circuit comprises a first multiplexer for selecting one of the voltages output from the first voltage dividing unit in response to the highest gamma register value.

3. The display device of claim 2 , wherein the highest gamma register value is used for representing black gradation.

4. The display device of claim 3 , wherein each of the R gamma voltage generator, the G gamma voltage generator, and the B gamma voltage generator includes the first multiplexer and generates a first gamma voltage.

5. The display device of claim 4 , wherein the first multiplexer included in one of the R gamma voltage generator, the G gamma voltage generator, and the B gamma voltage generator is supplied directly with the highest gamma register value which is different from the highest gamma register value directly supplied to the first multiplexer included in another of the R gamma voltage generator, the G gamma voltage generator, and the B gamma voltage generator.

6. The display device of claim 4 , wherein the data driver comprises: an R digital-to-analog converter (DAC) configured to generate an R black data voltage based on the first gamma voltage output from the R gamma voltage generator; a G DAC configured to generate a G black data voltage based on the first gamma voltage output from the G gamma voltage generator; and a B DAC configured to generate a B black data voltage based on the first gamma voltage output from the B gamma voltage generator.

7. The display device of claim 6 , wherein the G black data voltage output from the G DAC has a voltage level higher than the R black data voltage and the B black data voltage.

8. The display device of claim 6 , further comprising: a timing controller configured to control driving timings of the data driver and to control a duty ratio in proportional to a brightness value, wherein the data driver is configured to adjust one of the R black data voltage, the G black data voltage, and the B black data voltage to be larger in proportional to the brightness value.

9. The display device of claim 8 , wherein at least one of the pixels includes an organic light emitting diode emitting light in response to a driving current flowing from a driving transistor, and wherein a magnitude of a low potential driving voltage supplied to a cathode electrode of the organic light emitting diode is adjusted to be larger in proportional to the brightness value.

10. The display device of claim 1 , further comprising a gamma register configured to store a plurality of different gamma register values provided depending on gamma bands, wherein the highest gamma register value is included in the plurality of different gamma register values stored in the gamma register.

11. A driving device for driving a display device including a red (R) pixel, a green (G) pixel, and a blue (B) pixel, the driving device comprising: a gamma voltage generator configured to generate a plurality of gamma voltages, wherein the gamma voltage generator includes an R gamma voltage generator, a G gamma voltage generator, and a B gamma voltage generator, and wherein the R, G and B gamma voltage generators generate respectively R, G and B highest gamma voltages, and the R, G and B highest gamma voltages are different from each other; and a data driver configured to generate a first black data voltage, a second black data voltage, and a third black data voltage respectively based on the R, G and B highest gamma voltages, and supply the first, second and third black data voltages respectively to the R, G and B pixel, wherein one of the R, G and B gamma voltage generators is supplied with the highest gamma register value which is different from the highest gamma register value supplied to another of the R, G and B gamma voltage generators.

12. The driving device of claim 11 , wherein at least one of the R, G and B gamma voltage generators includes: a first voltage dividing unit configured to divide a reference voltage; a first voltage dividing circuit configured to generate the R, G or B highest gamma voltage by selecting voltages output from the first voltage dividing unit according to a highest gamma register value; and a second voltage dividing circuit configured to generate other gamma voltages using the reference voltage.

13. The driving device of claim 12 , wherein the first voltage dividing circuit comprises a first multiplexer for selecting one of the voltages output from the first voltage dividing unit in response to the highest gamma register value.

14. The driving device of claim 13 , wherein the highest gamma register value is used for representing black gradation.

15. The driving device of claim 12 , wherein each of the R gamma voltage generator, the G gamma voltage generator, and the B gamma voltage generator includes the first voltage dividing unit, the first voltage diving circuit and the second voltage diving circuit.

16. The driving device of claim 11 , wherein the data driver comprises: an R digital-to-analog; converter (DAC) configured to generate the first black data voltage based on the R highest gamma voltage; a G DAC configured to generate the second black data voltage based on the G highest gamma voltage; and a B DAC configured to generate the third black data voltage based on the B highest gamma voltage.

17. The driving device of claim 16 , wherein the second black data voltage output from the G DAC has a voltage level higher than the first and third black data voltages.

18. The driving device of claim 11 , further comprising: a timing controller configured to control driving timings of the data driver and to control a duty ratio in proportional to a brightness value, wherein the data driver is configured to adjust one of the first, second and third black data voltage to be larger in proportional to the brightness value.

19. The driving device of claim 18 , wherein at least one of the R, G and B pixels includes an organic light emitting diode emitting light in response to a driving current flowing from a driving transistor, and wherein a magnitude of a low potential driving voltage supplied to a cathode electrode of the organic light emitting diode is adjusted to be larger in proportional to the brightness value.

20. The driving device of claim 12 , further comprising a gamma register configured to store a plurality of different gamma register values provided depending on gamma bands, wherein the highest gamma register value is included in the plurality of different gamma register values stored in the gamma register.